Steam Generation Processes Utilizing Biomass Feedstocks

ABSTRACT

Integrated catalytic gasification processes are provided involving generating steam for converting carbonaceous materials to combustible gases, such as methane. Generally, steam generated from the combustion of a biomass is provided to a catalytic gasifier, wherein under appropriate temperature and pressure conditions, a carbonaceous feedstock is converted into a plurality of product gases, including, but not limited to, methane, carbon monoxide, hydrogen, and carbon dioxide.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §119 from U.S.Provisional Application Ser. No. 61/032,713 (filed Feb. 29, 2008), thedisclosure of which is incorporated by reference herein for all purposesas if fully set forth.

FIELD OF THE INVENTION

The present invention relates to methods for the production of steam foruse in a catalytic gasification reactor which have a reduced carbonfootprint. In particular, the present invention relates to the use ofbiomass for the generation of steam for use in the catalyticgasification of a carbonaceous material to yield, in particular,methane.

BACKGROUND OF THE INVENTION

In view of numerous factors such as higher energy prices andenvironmental concerns, the production of value-added gaseous productsfrom lower-fuel-value carbonaceous feedstocks, such as biomass, coal andpetroleum coke, is receiving renewed attention. The catalyticgasification of such materials to produce methane and other value-addedgases is disclosed, for example, in U.S. Pat. No. 3,828,474, U.S. Pat.No. 3,998,607, U.S. Pat. No. 4,057,512, U.S. Pat. No. 4,092,125, U.S.Pat. No. 4,094,650, U.S. Pat. No. 4,204,843, U.S. Pat. No. 4,468,231,U.S. Pat. No. 4,500,323, U.S. Pat. No. 4,541,841, U.S. Pat. No.4,551,155, U.S. Pat. No. 4,558,027, U.S. Pat. No. 4,606,105, U.S. Pat.No. 4,617,027, U.S. Pat. No. 4,609,456, U.S. Pat. No. 5,017,282, U.S.Pat. No. 5,055,181, U.S. Pat. No. 6,187,465, U.S. Pat. No. 6,790,430,U.S. Pat. No. 6,894,183, U.S. Pat. No. 6,955,695, US2003/0167961A1,US2006/0265953A1, US2007/000177A1, US2007/083072A1, US2007/0277437A1 andGB 1599932.

The process for the catalytic gasification of a carbonaceous material tosynthetic natural gas requires the presence of steam to react withcarbon to generate methane and carbon dioxide. It has generally beencontemplated to utilize coal-fired boilers to generate the requiredsteam. Such methods have the disadvantages of requiring an additionalfuel source for the boiler, while producing an exhaust comprising carbondioxide, which may be exhausted to the atmosphere, representing asubstantial carbon footprint for the process. As such, there exists aneed in the art to develop processes for the catalytic gasification ofcarbonaceous materials to synthetic natural gas which more efficientlyutilize fuels sources, including those utilized for generating steam,while decreasing the carbon footprint of the overall process.

SUMMARY OF THE INVENTION

In a first aspect, the invention provides a process for converting acarbonaceous feedstock into a plurality of gaseous products, the processcomprising the steps of: (A) supplying a biomass feedstock to a reactor;(B) at least partially combusting the biomass feedstock in the reactorin the presence of an oxygen-containing gas and under suitabletemperature and pressure to generate heat energy; (C) utilizing the heatenergy to generate steam; (D) introducing a carbonaceous feedstock, analkali metal gasification catalyst, and at least a portion of the steamto a gasifier; (E) reacting the carbonaceous feedstock in the gasifierin the presence of the steam and the alkali metal gasification catalystand under suitable temperature and pressure to form a gas streamcomprising a plurality of gaseous products comprising methane and atleast one or more of hydrogen, carbon monoxide, carbon dioxide, hydrogensulfide, ammonia and other higher hydrocarbons; and (F) at leastpartially separating the plurality of gaseous products to produce aproduct stream comprising a predominant amount of one of the gaseousproducts.

In a second aspect, the invention provides a process for converting acarbonaceous feedstock into a plurality of gaseous products, andgenerating electricity, the process comprising the steps of: (A)supplying a biomass feedstock to a reactor; (B) at least partiallycombusting the biomass feedstock in the reactor in the presence of anoxygen-containing gas and under suitable temperature and pressure togenerate heat energy; (C) utilizing the heat energy to generate steam;(D) dividing the steam into at least a first steam stream and a secondsteam stream; (E) introducing the first steam stream, a carbonaceousfeedstock and an alkali metal gasification catalyst to a gasifier; (F)introducing the second steam stream to a steam turbine to generateelectricity; (G) reacting the carbonaceous feedstock in the gasifier inthe presence of the first steam stream and the alkali metal gasificationcatalyst and under suitable temperature and pressure to form a gasstream comprising a plurality of gaseous products comprising methane andat least one or more of hydrogen, carbon monoxide, carbon dioxide,hydrogen sulfide, ammonia and other higher hydrocarbons; (H) at leastpartially separating the plurality of gaseous products to produce aproduct stream comprising a predominant amount of one of the gaseousproducts.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow chart illustrating a method for generating combustiblegases according to an embodiment of the present invention.

DETAILED DESCRIPTION

The present invention relates to methods for generating steam forproviding to a catalytic gasification reactor, which methods result inreduced carbon footprints. Such methods can be integrated into processesfor the catalytic gasification of a carbonaceous feedstock and/or forgenerating electricity.

The present invention can be practiced, for example, using any of thedevelopments to catalytic gasification technology disclosed in commonlyowned US2007/0000177A1, US2007/0083072A1 and US2007/0277437A1; and U.S.patent application Ser. No. 12/178,380 (filed 23 Jul. 2008), Ser. No.12/234,012 (filed 19 Sep. 2008) and Ser. No. 12/234,018 (filed 19 Sep.2008). All of the above are incorporated by reference herein for allpurposes as if fully set forth.

Moreover, the present invention can be practiced in conjunction with thesubject matter of the following U.S. Patent Applications, each of whichwas filed on Dec. 28, 2008: Ser. No. 12/342,554, entitled “CATALYTICGASIFICATION PROCESS WITH RECOVERY OF ALKALI METAL FROM CHAR”; Ser. No.12/342,565, entitled “PETROLEUM COKE COMPOSITIONS FOR CATALYTICGASIFICATION”; Ser. No. 12/342,578, entitled “COAL COMPOSITIONS FORCATALYTIC GASIFICATION”; Ser. No. 12/342,596, entitled “PROCESSES FORMAKING SYNTHESIS GAS AND SYNGAS-DERIVED PRODUCTS”; Ser. No. 12/342,608,entitled “PETROLEUM COKE COMPOSITIONS FOR CATALYTIC GASIFICATION”; Ser.No. 12/342,628, entitled “PROCESSES FOR MAKING SYNGAS-DERIVED PRODUCTS”;Ser. No. 12/342,663, entitled “CARBONACEOUS FUELS AND PROCESSES FORMAKING AND USING THEM”; Ser. No. 12/342,715, entitled “CATALYTICGASIFICATION PROCESS WITH RECOVERY OF ALKALI METAL FROM CHAR”; Ser. No.12/342,736, entitled “CATALYTIC GASIFICATION PROCESS WITH RECOVERY OFALKALI METAL FROM CHAR”; Ser. No. 12/343,143, entitled “CATALYTICGASIFICATION PROCESS WITH RECOVERY OF ALKALI METAL FROM CHAR”; Ser. No.12/343,149, entitled “STEAM GENERATING SLURRY GASIFIER FOR THE CATALYTICGASIFICATION OF A CARBONACEOUS FEEDSTOCK”; and Ser. No. 12/343,159,entitled “CONTINUOUS PROCESSES FOR CONVERTING CARBONACEOUS FEEDSTOCKINTO GASEOUS PRODUCTS”. All of the above are incorporated by referenceherein for all purposes as if fully set forth.

Further, the present invention can be practiced in conjunction with thesubject matter of the following U.S. Patent Applications, each of whichwas filed concurrently herewith: Ser. No. ______, entitled “PROCESSESFOR MAKING ABSORBENTS AND PROCESSES FOR REMOVING CONTAMINANTS FROMFLUIDS USING THEM” (attorney docket no. FN-0019 US NP1); Ser. No.______, entitled “REDUCED CARBON FOOTPRINT STEAM GENERATION PROCESSES”(attorney docket no. FN-0021 US NP1); Ser. No. ______, entitled “PROCESSAND APPARATUS FOR THE SEPARATION OF METHANE FROM A GAS STREAM” (attorneydocket no. FN-0022 US NP1); Ser. No. ______, entitled “SELECTIVE REMOVALAND RECOVERY OF ACID GASES FROM GASIFICATION PRODUCTS” (attorney docketno. FN-0023 US NP1); Ser. No. ______, entitled “COAL COMPOSITIONS FORCATALYTIC GASIFICATION” (attorney docket no. FN-0024 US NP1); Ser. No.______, entitled “COAL COMPOSITIONS FOR CATALYTIC GASIFICATION”(attorney docket no. FN-0025 US NP1); Ser. No. ______, entitled “CO-FEEDOF BIOMASS AS SOURCE OF MAKEUP CATALYSTS FOR CATALYTIC COALGASIFICATION” (attorney docket no. FN-0026 US NP1); Ser. No. ______,entitled “COMPACTOR-FEEDER” (attorney docket no. FN-0027 US NP1); Ser.No. ______, entitled “CARBONACEOUS FINES RECYCLE” (attorney docket no.FN-0028 US NP1); Ser. No. ______, entitled “BIOMASS CHAR COMPOSITIONSFOR CATALYTIC GASIFICATION” (attorney docket no. FN-0029 US NP1); Ser.No. ______, entitled “CATALYTIC GASIFICATION PARTICULATE COMPOSITIONS”(attorney docket no. FN-0030 US NP1); and Ser. No. ______, entitled“BIOMASS COMPOSITIONS FOR CATALYTIC GASIFICATION” (attorney docket no.FN-0031 US NP1). All of the above are incorporated herein by referencefor all purposes as if fully set forth.

All publications, patent applications, patents and other referencesmentioned herein, if not otherwise indicated, are explicitlyincorporated by reference herein in their entirety for all purposes asif fully set forth.

Unless otherwise defined, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs. In case of conflict, thepresent specification, including definitions, will control.

Except where expressly noted, trademarks are shown in upper case.

Although methods and materials similar or equivalent to those describedherein can be used in the practice or testing of the present invention,suitable methods and materials are described herein.

Unless stated otherwise, all percentages, parts, ratios, etc., are byweight.

When an amount, concentration, or other value or parameter is given as arange, or a list of upper and lower values, this is to be understood asspecifically disclosing all ranges formed from any pair of any upper andlower range limits, regardless of whether ranges are separatelydisclosed. Where a range of numerical values is recited herein, unlessotherwise stated, the range is intended to include the endpointsthereof, and all integers and fractions within the range. It is notintended that the scope of the present invention be limited to thespecific values recited when defining a range.

When the term “about” is used in describing a value or an end-point of arange, the invention should be understood to include the specific valueor end-point referred to.

As used herein, the terms “comprises,” “comprising,” “includes,”“including,” “has,” “having” or any other variation thereof, areintended to cover a non-exclusive inclusion. For example, a process,method, article, or apparatus that comprises a list of elements is notnecessarily limited to only those elements but can include otherelements not expressly listed or inherent to such process, method,article, or apparatus. Further, unless expressly stated to the contrary,“or” refers to an inclusive or and not to an exclusive or. For example,a condition A or B is satisfied by any one of the following: A is true(or present) and B is false (or not present), A is false (or notpresent) and B is true (or present), and both A and B are true (orpresent).

The use of “a” or “an” to describe the various elements and componentsherein is merely for convenience and to give a general sense of theinvention. This description should be read to include one or at leastone and the singular also includes the plural unless it is obvious thatit is meant otherwise.

The materials, methods, and examples herein are illustrative only and,except as specifically stated, are not intended to be limiting.

Steam Generation Methods

The steam generating processes of the present invention are particularlyuseful in an integrated catalytic gasification process for convertingcarbonaceous materials to combustible gases, such as methane, whileachieving a low or near zero carbon footprint. In some cases, the carbonfootprint may be negative if the exhaust gas produced from the steamgeneration processes are directed through the catalytic gasificationprocesses, as described herein.

A typical flow chart for integration into a process for generating acombustible gas from a carbonaceous feedstock is illustrated in FIG. 1,and referenced herein. Generally, steam and a carbonaceous feedstock areprovided to a gasifier (200), wherein under appropriate temperature andpressure conditions, and in the presence of one or more gasificationcatalysts, the carbonaceous feedstock is converted into a plurality ofproduct gases, including, but not limited to, methane, carbon monoxide,hydrogen, carbon dioxide, ammonia, and hydrogen sulfide.

In the present processes, the steam provided to the gasifier (200) isgenerated from action of reactor (100) and is conveyed via a heated gasconduit (110) from the reactor to the catalytic gasifier (200). Reactor(100) includes, but is not limited to, commercial gasification reactors,oxy-fuel combustors, and boilers. Reactor (100) is fed with a biomassfeedstock (404), from a feedstock preparation operation (400), andgenerally, may comprise one or a mixture of biomass materials, asdefined herein.

The partial or complete gasification or partial or complete combustionof the biomass feedstock (404) in reactor (100) generates large amountsof heat energy and an exhaust gas comprising carbon dioxide.

Advantageously, this heat energy can be used to contact any type of heatexchanger, in contact with a water source, to generate steam. Forexample, any of the boilers known to those skilled in the art can befueled by the biomass feedstock (404) to supply steam to gasifier (200).While any water source can be used to generate steam, the water commonlyused in known boiler systems is purified and deionized (about 0.3-1.0μS/cm) so that corrosive processes are slowed. Such boilers can bepowered, for example, through the oxygen-blown combustion of any biomassmaterial. Ultimately, the thermal energy from the gasification orcombustion of the biomass feedstock (404) may heat a water source incommunication with reactor (100), to produce steam (typically at about1300° F. and 500 psi).

The steam produced by action of the reactor (100) can be generallyvariable based on the type of reactor and feedstock being utilized.Preferably, the steam can be provided to the catalytic gasifier in therange of about 550 to about 600 psia and about 1300 to about 1400° F.(about 700 to about 760° C.). More preferably, reactor (100) producessteam at a pressure essentially the same as the conditions beingutilized in the catalytic gasifier (200), as any excess heat can be moreefficiently captured for use in other operations (e.g., feedstockdrying).

In another example, the contacting of water with the heat energy toproduce steam may occur within reactor (100) either by the addition ofwater to the reactor via a separate feed line (not shown in FIG. 1), orby supplying the biomass feedstock (404), for example, as an aqueousslurry comprising a biomass particulate. In such cases, the steam can begenerated as a gaseous mixture further comprising either (i) carbondioxide, when reactor (100) is a combustor; or (ii) carbon monoxide,hydrogen and (optionally) carbon dioxide when reactor (100) is agasifier. For example, steam can be generated within a gasifier whichproduces steam and synthesis gas from an aqueous biomass slurry, such asdescribed in previously incorporated U.S. patent application Ser. No.12/343,149.

The steam generated by reactor (100) may be routed, in whole or in part,into one or more heated conduits (105), which may be located at or nearan exit conduit carrying the combustion gases, when present. Forexample, the steam can be divided into a plurality of steam streams(e.g., into at least a first and second steam stream), each comprising aportion of the steam. The portion of the steam which is provided to eachstream may be controlled according to methods known in the art. Eachsteam stream can be routed in a variety of directions. For example, oneor more steam streams may be provided the gasification reactor via aheated conduit (110); or one or more steam streams can be used to dry acarbonaceous feedstock (e.g., via heated conduit 130); or one or moresteam streams can be routed to a steam turbine (2000, via heated conduit140) for generation of electricity (2001). In order to avoid excessivecooling of the steam during transport, the contents of the heatedconduits may be superheated according to methods known to those skilledin the art (e.g., via contact with a heat exchanger) prior to deliveryof the steam to any endpoint. In one particular example, all the steamgenerated from reactor (100) is provided to gasifier (200).

A separate exhaust gas may be generated from combustion of the biomassfeedstock in reactor (100), which may be (i) exhausted from the process;(ii) supplied with the generated steam via heated conduit (110) togasifier (200); or (ii) supplied to gasifier (200) via a second heatedconduit (120) (i.e., the exit conduit). By optionally directing theexhaust gas from reactor (100) through the catalytic gasifier (200) andthe associated gas purification and separation unit operations (infra),essentially all the carbon dioxide produced from the steam generationprocess as well as from the gasification of a carbonaceous material maybe recovered, yielding an overall catalytic gasification process havinga near zero, or possibly negative, carbon footprint.

By “carbon footprint”, reference is made to the carbon dioxide releasedinto the environment from non-biomass sources, for example, from thecombustion of fossil fuels and release of the resulting carbon dioxideinto the atmosphere. Capture and sequestration of all carbon dioxidegenerated from non-biomass sources would be considered to have a neutralcarbon footprint, as no carbon dioxide would have been released into theatmosphere.

By contrast, the release of carbon dioxide into the atmosphere frombiomass sources is considered carbon footprint neutral, since biomass iscreated (for example, directly as a plant, or indirectly as part of thefood chain) by the capture and conversion of carbon dioxide from theatmosphere. As such, the capture and sequestration of carbon dioxidegenerated from biomass sources can actually result in a negative(reduced) carbon footprint.

Steam can also be supplied from a second gasification reactor (100)coupled with a combustion turbine, the exhaust gas of which contacts aheat exchanger in contact with a water source (e.g., a boiler system),to produce steam. The steam and exhaust gas (from the combustionturbine) may be directed as discussed previously.

Recycled steam from other process operations can also be used forsupplementing steam to the catalytic gasifier. For example, in thepreparation of a particulate carbonaceous feedstock, when a slurriedparticulate composition is dried with a fluid bed slurry drier, asdiscussed below, then the generated steam may be fed to the catalyticgasification reactor (200).

The small amount of required heat input for the catalytic gasifier (200)can be provided by, for example, superheating the steam provided to thegasifier; or superheating a mixture of the steam and any second gassource feeding the gasification reactor (e.g., the exhaust from reactor(100)). In one embodiment, compressed recycle gas comprising CO and H₂(902, infra) can be mixed with the steam and the resulting steam/recyclegas mixture can be further superheated by heat exchange with thecatalytic gasifier effluent followed by superheating in a recycle gasfurnace for introduction into gasifier (200).

Catalytic Gasification Methods

Catalytic gasifier (200) utilizes a gas comprising steam, andoptionally, other gases such as oxygen or air, carbon monoxide andhydrogen, for pressurization and reactions of the carbonaceousfeedstock. The catalytic gasification reactor (200) can be operated atmoderately high pressures and temperature. Typically, a carbonaceousfeedstock (405) and a gasification catalyst (e.g., an alkali metalgasification catalyst) are introduced to a reaction zone of thecatalytic gasifier (200) while maintaining the required temperature,pressure, and flow rate of the feedstock. Those skilled in the art arefamiliar with feed systems for providing feedstocks to high pressureand/or temperature environments, including, star feeders, screw feeders,rotary pistons, and lock-hoppers. It should be understood that the feedsystem can include two or more pressure-balanced elements, such as lockhoppers, which would be used alternately.

The carbonaceous feedstock and gasification catalyst may be introducedseparately or combined as a catalyzed feedstock (infra) and are providedto the catalytic gasifier (200) from a feedstock preparation operation(400). In some instances, the carbonaceous feedstock (405) can beprepared at pressures conditions above the operating pressure ofcatalytic gasifier. Hence, the carbonaceous feedstock (405) may bedirectly passed into the catalytic gasifier without furtherpressurization.

Any of several catalytic gasifiers (200) can be utilized in the processof the described herein. Suitable gasifiers include, but are not limitedto, counter-current fixed bed, co-current fixed bed, fluidized bed,entrained flow, and moving bed reactors. A catalytic gasifier forgasifying liquid feeds, such as liquid petroleum residues, is disclosedin previously incorporated U.S. Pat. No. 6,955,695.

The pressure in the catalytic gasifier (200) typically can be from about10 to about 100 atm (from about 150 to about 1500 psig). Thegasification reactor temperature can be maintained around at least about450° C., or at least about 600° C., or at least about 900° C., or atleast about 750° C., or about 600° C. to about 700° C.; and at pressuresof at least about 50 psig, or at least about 200 psig, or at least about400 psig, to about 1000 psig, or to about 700 psig, or to about 600psig.

In one embodiment, an optional methane reformer (1000) may be includedin the process. For example, when reactor (100) is a gasificationreactor, a methane reformer (1000) may supplement the recycle CO and H₂stream, the exhaust gas (120, as shown in FIG. 1) and/or steam stream(110) from the reactor to ensure that enough recycle gas is supplied tothe reactor so that the net heat of reaction is as close to neutral aspossible (only slightly exothermic or endothermic), in other words, thatthe catalytic gasifier is run under substantially thermally neutralconditions. In such instances, methane (901 a) can be supplied for thereformer from the methane product (901), as described below.

Reaction of the carbonaceous feedstock (405) in the catalytic gasifier(200), in the presence of one or more gasification catalysts under thedescribed conditions, provides a crude product gas. When the exhaust gas(120) from reactor (100) is provided in whole to the gasifier (200), thecrude product gas can comprise essentially all the carbon dioxideproduced from reactor (100) and gasifier (200). Additionally, bothreactor (100) and gasifier (200) produce a char (102 and 202,respectively).

The char produced in the catalytic gasifier (202) is typically removedfrom the gasifier for sampling, purging, and/or catalyst recovery in acontinuous or batch-wise manner. Methods for removing char are wellknown to those skilled in the art. One such method taught byEP-A-0102828, for example, can be employed. The char can be periodicallywithdrawn from the catalytic gasification reactor through a lock hoppersystem, although other methods are known to those skilled in the art.

Often, the char (202) is directed to a catalyst recovery and recycleprocess (300) to produce a recycled catalyst stream (301) and a depletedchar. Processes have been developed to recover alkali metal from thesolid purge in order to reduce raw material costs and to minimizeenvironmental impact of a catalytic gasification process. For example,the char (202) can be quenched with recycle gas and water and directedto a catalyst recycling operation for extraction and reuse of the alkalimetal catalyst. Particularly useful recovery and recycling processes aredescribed in U.S. Pat. No. 4,459,138, as well as previously incorporatedU.S. Pat. No. 4,057,512 and US2007/0277437A1, and previouslyincorporated U.S. patent application Ser. Nos. 12/342,554, 12/342,715,12/342,736 and 12/343,143. Reference can be had to those documents forfurther process details.

Upon completion of catalyst recovery, the recovered catalyst stream(301) (as a solution or solid) may be directed to the second feedstockpreparation unit (403) of the feedstock preparation operation (400), asdescribed herein. The depleted char may be utilized as a co-feedstockfor reactor (100) (not shown in FIG. 1).

The char (102) produced in reactor (100) is typically removed viasimilar methods to those described for the catalytic gasificationreactor, and may be recovered and extracted to provide a leachate forpreparing the carbonaceous feedstock (405), as described in previouslyincorporated U.S. patent application Ser. No. ______, entitled“CATALYTIC GASIFICATION PARTICULATE COMPOSITIONS” (attorney docket no.FN-0030 US NP1); or may be recovered and utilized, itself, as part ofthe second carbonaceous feedstock (405), as described in previouslyincorporated U.S. patent application Ser. No. ______, entitled “BIOMASSCHAR COMPOSITIONS FOR CATALYTIC GASIFICATION” (attorney docket no.FN-0029 US NP1).

Crude product gas effluent leaving the catalytic gasifier (200) can passthrough a portion of the reactor which serves as a disengagement zonewhere particles too heavy to be entrained by the gas leaving the reactor(i.e., fines) are returned to the fluidized bed. The disengagement zonecan include one or more internal cyclone separators or similar devicesfor removing fines and particulates from the gas. The gas effluent (201)passing through the disengagement zone and leaving the catalyticgasifier generally contains CH₄, CO₂, H₂ and CO, H₂S, NH₃, other higherhydrocarbons, unreacted steam, entrained fines, and other contaminantssuch as COS.

The gas stream from which the fines have been removed (201) can then bepassed through a heat exchanger (500) to cool the gas and the recoveredheat can be used to preheat recycle gas and generate high pressure steam(501). Residual entrained fines can also be removed by any suitablemeans such as external cyclone separators, optionally followed byVenturi scrubbers. The recovered fines can be processed to recoveralkali metal catalyst then passed to the feedstock preparation process(400), returned to the catalytic gasification reactor, or directlyrecycled back to feedstock preparation as described in previouslyincorporated U.S. patent application Ser. No. ______, entitled“CARBONACEOUS FINES RECYCLE” (attorney docket no. FN-0028 US NP1).

The gas stream (502) from which the fines have been removed can be fedto a gas purification operation (600) comprising COS hydrolysis reactors(601) for COS removal (sour process) and further cooled in a heatexchanger to recover residual heat prior to entering water scrubbers(602) for ammonia recovery, yielding a scrubbed gas comprising at leastH₂S, CO₂, CO, H₂, and CH₄. Methods for COS hydrolysis are known to thoseskilled in the art, for example, see U.S. Pat. No. 4,100,256. Theresidual heat from the scrubbed gas can be used to generate low pressuresteam.

Scrubber water (605) and sour process condensate (604) can be processedto strip and recover H₂S, CO₂ and NH₃; such processes are well known tothose skilled in the art. NH₃ can typically be recovered as an aqueoussolution (e.g., 20 wt %). Alternatively, scrubber water (605) and sourprocess condensate (604) can be returned to reactor (100), therebyreducing overall process water usage and eliminating separate cleanup ofthese process streams.

A subsequent acid gas removal process (603) can be used to remove H₂Sand CO₂ from the scrubbed gas stream by a physical absorption methodinvolving solvent treatment of the gas to give a cleaned gas stream.Such processes involve contacting the scrubbed gas with a solvent suchas monoethanolamine, diethanolamine, methyldiethanolamine,diisopropylamine, diglycolamine, a solution of sodium salts of aminoacids, methanol, hot potassium carbonate or the like. One method caninvolve the use of Selexol® (UOP LLC, Des Plaines, Ill. USA) orRectisol® (Lurgi AG, Frankfurt am Main, Germany) solvent having twotrains; each train consisting of an H₂S absorber and a CO₂ absorber. Thespent solvent(s) (607) containing H₂S, CO₂ and other contaminants can beregenerated by any method known to those skilled in the art, includingcontacting the spent solvent with steam or other stripping gas to removethe contaminants or by passing the spent solvent through strippercolumns. Recovered acid gases can be sent for sulfur recoveryprocessing; for example, any recovered H₂S from the acid gas removal andsour water stripping can be converted to elemental sulfur by any methodknown to those skilled in the art, including the Claus process. Sulfurcan be recovered as a molten liquid. Stripped water can be directed forrecycled use in preparation of the first and/or particulate carbonaceousfeedstock. One method for removing acid gases from the scrubbed gasstream is described in previously incorporated U.S. patent applicationSer. No. ______, entitled “SELECTIVE REMOVAL AND RECOVERY OF ACID GASESFROM GASIFICATION PRODUCTS” (attorney docket no. FN-0023 US NP1).

Advantageously, CO₂ generated in the integrated process, whether in thesteam generation or catalytic gasification or both, can be recovered forsubsequent use or sequestration, enabling a greatly decreased carbonfootprint. Steam may be generated with a reduced carbon footprint asdescribed in previously incorporated U.S. patent application Ser. No.______, entitled “REDUCED CARBON FOOTPRINT STEAM GENERATION PROCESSES”(attorney docket no. FN-0021 US NP1).

The resulting cleaned gas stream (606) exiting the gas purificationoperation (600) contains mostly CH₄, H₂, and CO and, typically, smallamounts of CO₂ and H₂O. The cleaned gas stream (606) can be furtherprocessed to separate and recover CH₄ by any suitable gas separationmethod (900) known to those skilled in the art including, but notlimited to, cryogenic distillation and the use of molecular sieves orceramic membranes, or via the generation of methane hydrate as disclosedin previously incorporated U.S. patent application Ser. No. ______,entitled “PROCESS AND APPARATUS FOR THE SEPARATION OF METHANE FROM A GASSTREAM” (attorney docket no. FN-0022 US NP1).

Typically, two gas streams can be produced by the gas separation process(900), a methane product stream (901) and a syngas stream (902, H₂ andCO). The syngas stream (902) can be compressed and recycled. One optioncan be to recycle the syngas steam directly to the catalytic gasifier(200). In one case, the recycled syngas is combined with the exhaust gas(120) from the reactor (100), and the mixture introduced into thecatalytic gasification reactor. In another case, the recycled syngas(902) can be directed into reactor (100). When a fluid bed reactor isutilized for reactor (100), the syngas may provide fluidization or aidin fluidization of the reaction bed.

If necessary, a portion of the methane product (901 a) can be directedto a reformer, as discussed previously. The need to direct a portion ofthe methane product can be controlled, for example, by the ratio of COto H₂ in the exhaust gas from reactor (100). Particularly, methane canbe directed to a reformer (1000) to supplement (1001) the exhaust gas(120) supplied to the catalytic gasification reactor and, in someinstance, provide a ratio of about 3:1 of H₂ to CO in the feed to thecatalytic gasification reactor (200). A portion of the methane productcan also be used as plant fuel for a gas turbine.

Biomass and Carbonaceous Feedstocks

The biomass feedstock supplied to the reactor (100) comprises any one orcombination of biomasses. The carbonaceous feedstock may comprise anyone or combination of non-biomass materials and/or any one orcombination of biomass materials. Each of the biomass feedstock andcarbonaceous feedstocks may comprise the same or different biomasses,when present. In one embodiment, the biomass, carbonaceous, or bothfeedstocks comprise biomass. In another embodiment, the carbonaceousfeedstock comprises non-biomass carbonaceous material. In yet anotherembodiment, the carbonaceous feedstock comprises biomass and non-biomasscarbonaceous material.

The biomass feedstock and carbonaceous feedstock may be supplied as aparticulate. Each feedstock, independently, may have an average particlesize of from about 25 microns, or from about 45 microns, up to about500, or up to about 2500 microns. One skilled in the art can readilydetermine the appropriate particle size for the individual particulatesand the biomass feedstock and particulate carbonaceous feedstocks. Forexample, when a fluid bed gasification reactor is used as reactor (100)and/or gasifier (200), the biomass feedstock and/or particulatecarbonaceous feedstock can have an average particle size which enablesincipient fluidization of the carbonaceous feedstock at the gas velocityused in the fluid bed gasification reactor.

The term “carbonaceous material” as used herein refers to anycarbonaceous material including, but not limited to biomass, coal,petroleum coke, asphaltenes, liquid petroleum residues, used motor oiland other waste processed petroleum sources, untreated or treated sewagewaste, garbage, plastics, wood and other biomass, or mixtures thereof.The carbonaceous materials for the feedstock can comprise carbon sourcescontaining at least about 20%, or at least about 30%, or at least about40%, or at least about 50%, or at least about 60%, or at least about70%, or at least about 80% carbon by dry weight.

The term “biomass” as used herein refers to carbonaceous materialsderived from recently (for example, within the past 100 years) livingorganisms, including plant-based biomass and animal-based biomass. Forclarification, biomass does not include fossil-based carbonaceousmaterials, such as coal.

The term “plant-based biomass” as used herein means materials derivedfrom green plants, crops, algae, and trees, such as, but not limited to,sweet sorghum, bagasse, sugarcane, bamboo, hybrid poplar, hybrid willow,albizia trees, eucalyptus, alfalfa, clover, oil palm, switchgrass,sudangrass, millet, jatropha, and miscanthus (e.g.,Miscanthus×giganteus). Biomass further include wastes from agriculturalcultivation, processing, and/or degradation such as corn cobs and husks,corn stover, straw, nut shells, vegetable oils, canola oil, rapeseedoil, biodiesels, tree bark, wood chips, sawdust, and yard wastes.

The term “animal-based biomass” as used herein means wastes generatedfrom animal cultivation and/or utilization. For example, biomassincludes, but is not limited to, wastes from livestock cultivation andprocessing such as animal manure, guano, poultry litter, animal fats,and municipal solid wastes (e.g., sewage).

The term “non-biomass”, as used herein, means those carbonaceousmaterials which are not encompassed by the term “biomass” as definedherein. For example, non-biomass includes, but is not limited to,anthracite, bituminous coal, sub-bituminous coal, lignite, petroleumcoke, asphaltenes, liquid petroleum residues, or mixtures thereof.

The term “petroleum coke” as used herein includes (i) the solid thermaldecomposition product of high-boiling hydrocarbon fractions obtained inpetroleum processing (heavy residues); and (ii) the solid thermaldecomposition product of processing tar sands (bituminous sands or oilsands) Such carbonization products include, for example, green,calcined, needle and fluidized bed petroleum coke. Petroleum coke isgenerally prepared via delayed coking or fluid coking. The petroleumcoke can be residual material remaining after retorting tar sands (e.g.,mined) are heated to extract any oil.

Resid petcoke can also be derived from a crude oil, for example, bycoking processes used for upgrading heavy-gravity residual crude oil,which petroleum coke contains ash as a minor component, typically about1.0 wt % or less, and more typically about 0.5 wt % of less, based onthe weight of the coke. Typically, the ash in such lower-ash cokespredominantly comprises metals such as nickel and vanadium.

Tar sands petcoke can be derived from an oil sand, for example, bycoking processes used for upgrading oil sand. Tar sands petcoke containsash as a minor component, typically in the range of about 2 wt % toabout 12 wt %, and more typically in the range of about 4 wt % to about12 wt %, based on the overall weight of the tar sands petcoke.Typically, the ash in such higher-ash cokes predominantly comprisesmaterials such as compounds of silicon and/or aluminum.

The petroleum coke can comprise at least about 70 wt % carbon, at leastabout 80 wt % carbon, or at least about 90 wt % carbon, based on thetotal weight of the petroleum coke. Typically, the petroleum cokecomprises less than about 20 wt % percent inorganic compounds, based onthe weight of the petroleum coke.

The term “liquid petroleum residue” as used herein includes both (i) theliquid thermal decomposition product of high-boiling hydrocarbonfractions obtained in petroleum processing (heavy residues—“resid liquidpetroleum residue”) and (ii) the liquid thermal decomposition product ofprocessing tar sands (bituminous sands or oil sands—“tar sands liquidpetroleum residue”). The liquid petroleum residue is substantiallynon-solid; for example, it can take the form of a thick fluid or asludge.

Resid liquid petroleum residue also can be derived from a crude oil, forexample, by processes used for upgrading heavy-gravity crude oildistillation residue. Such liquid petroleum residue contains ash as aminor component, typically about 1.0 wt % or less, and more typicallyabout 0.5 wt % of less, based on the weight of the residue. Typically,the ash in such lower-ash residues predominantly comprises metals suchas nickel and vanadium.

Tar sands liquid petroleum residue can be derived from an oil sand, forexample, by processes used for upgrading oil sand. Tar sands liquidpetroleum residue contains ash as a minor component, typically in therange of about 2 wt % to about 12 wt %, and more typically in the rangeof about 4 wt % to about 12 wt %, based on the overall weight of theresidue. Typically, the ash in such higher-ash residues predominantlycomprises materials such as compounds of silicon and/or aluminum.

The term “coal” as used herein means peat, lignite, sub-bituminous coal,bituminous coal, anthracite, graphite, or mixtures thereof. In certainembodiments, the coal has a carbon content of less than about 85%, orless than about 80%, or less than about 75%, or less than about 70%, orless than about 65%, or less than about 60%, or less than about 55%, orless than about 50% by weight, based on the total coal weight. In otherembodiments, the coal has a carbon content ranging up to about 85%, orup to about 80%, or up to about 75% by weight, based on total coalweight. Examples of useful coals include, but are not limited to,Illinois #6, Pittsburgh #8, Beulah (N.D.), Utah Blind Canyon, and PowderRiver Basin (PRB) coals. Anthracite, bituminous coal, sub-bituminouscoal, and lignite coal may contain about 10 wt %, from about 5 to about7 wt %, from about 4 to about 8 wt %, and from about 9 to about 11 wt %,ash by total weight of the coal on a dry basis, respectively. However,the ash content of any particular coal source will depend on the rankand source of the coal, as is familiar to those skilled in the art (see,for example, Coal Data: A Reference, Energy Information Administration,Office of Coal, Nuclear, Electric and Alternate Fuels, U.S. Departmentof Energy, DOE/EIA-0064(93), February 1995).

Asphaltenes typically comprise aromatic carbonaceous solids at roomtemperature, and can be derived, from example, from the processing ofcrude oil, oil shale, bitumen, and tar sands.

Catalyst Components

As noted above, the carbonaceous feedstock and gasification catalyst canbe introduced to gasifier (200) separately or combined as a singlecatalyzed feedstock. Suitable gasification catalysts include, but arenot limited to, alkali metals such as lithium, sodium, potassium,rubidium, cesium, and mixtures thereof. Particularly useful arepotassium sources. Suitable alkali metal compounds include alkali metalcarbonates, bicarbonates, formates, oxalates, amides, hydroxides,acetates, or similar compounds. For example, the catalyst can compriseone or more of Na₂CO₃, K₂CO₃, Rb₂CO₃, Li₂CO₃, Cs₂CO₃, NaOH, KOH, RbOH orCsOH, and particularly, potassium carbonate and/or potassium hydroxide.

The carbonaceous feedstock, in certain embodiments, further comprises anamount of an alkali metal component, as an alkali metal and/or an alkalimetal compound, as well as optional co-catalysts, as disclosed in theprevious incorporated references. Typically, the quantity of the alkalimetal component in the composition is sufficient to provide a ratio ofalkali metal atoms to carbon atoms ranging from about 0.01, or fromabout 0.02, or from about 0.03, or from about 0.04, to about 0.06, or toabout 0.07, or to about 0.08. Further, the alkali metal is typicallyloaded onto a biomass or carbonaceous material to achieve an alkalimetal content of from about 3 to about 10 times more than the combinedash content of the biomass or carbonaceous material (e.g., coal and/orpetroleum coke), on a mass basis.

Methods for Preparing Biomass Feedstock

The biomass feedstock (404) comprises a particulate composition of oneor more biomasses; while the carbonaceous feedstock (405) may compriseone or more non-biomass materials, optionally in combination with one ormore biomass materials (i.e., one or more carbonaceous materials) and analkali metal gasification catalyst.

Each of the carbonaceous materials (i.e., biomass and/or non-biomass)can each be separately crushed and/or ground according to any methodsknown in the art in a first feedstock preparation unit (401), such asvia impact crushing and wet or dry grinding to yield particulates ofeach. Additional feedstock processing steps may be necessary dependingon the qualities of the carbonaceous materials. For example, manybiomasses, such as sewage, and carbonaceous materials containing highmoisture levels, such as high-moisture coals, can require drying priorto crushing. Further, some caking coals can be partially oxidizedaccording to methods known in the art to simplify gasification reactoroperation. Depending on the method utilized for crushing and/or grindingof the materials, the resulting particulates can be sized (i.e.,separated according to size) to provide an appropriate feedstock.

Any method known to those skilled in the art can be used to size theparticulates. For example, sizing can be preformed by screening orpassing the particulates through a screen or number of screens.Screening equipment can include grizzlies, bar screens, and wire meshscreens. Screens can be static or incorporate mechanisms to shake orvibrate the screen. Alternatively, classification can be used toseparate the particulates. Classification equipment can include oresorters, gas cyclones, hydrocyclones, rake classifiers, rotatingtrommels, or fluidized classifiers. The carbonaceous materials can bealso sized or classified prior to grinding and/or crushing.

In one example, coal is typically wet ground and sized (e.g., to aparticle size distribution of about 25 to 2500 microns) and then drainedof its free water (i.e., dewatered) to a wet cake consistency. Examplesof suitable methods for the wet grinding, sizing, and dewatering areknown to those skilled in the art; for example, see previouslyincorporated U.S. patent application Ser. No. 12/178,380.

The biomass feedstock comprises one or more types of biomass that may beblended as can be determined by one skilled in the art to provide thebiomass feedstock to reactor (100) depending on the nature of reactor(100; i.e., whether it is an oxy-combustor or gasifier). In variousembodiments, the biomass feedstock may comprise an aqueous slurry of thebiomass particulates (supra) and can be readily prepared by adding waterto the particulates before or after blending, as necessary.

The carbonaceous materials can be treated to associate at least a firstcatalyst (e.g., gasification catalyst) therewith, to provide thecarbonaceous feedstock (405) (i.e., catalyzed feedstock) for thegasifier (200). The materials (402) prepared in first feedstockpreparation unit (401) may be provided to a second feedstock preparationunit (403), either as individual streams or a previously blended stream,wherein an alkali metal catalyst may be provided to any one or more ofthe streams or the blended stream. Any methods known to those skilled inthe art can be used to associate one or more gasification catalysts withthe materials. Such methods include but are not limited to, admixingwith a solid catalyst source, impregnating the catalyst onto thecarbonaceous material or the biomass according to, for example,incipient wetness impregnation, evaporative impregnation, vacuumimpregnation, dip impregnation, and combinations of these methods.Gasification catalysts can be impregnated by slurrying the materialswith a solution (e.g., aqueous) of the catalyst.

In some cases, a second catalyst (e.g., co-catalyst) can be provided; insuch instances, the particulates can be treated in separate processingsteps to provide the first catalyst and second catalysts according toany of the preceding processes. For example, the primary gasificationcatalyst can be supplied (e.g., a potassium and/or sodium source),followed by a separate treatment to provide a co-catalyst source.Alternatively, the first and second catalysts can be provided as amixture in a single treatment; or the first and second catalysts can beprovided to separate materials and the treated materials ultimatelyblended.

One particular method suitable for combining coals with the gasificationcatalysts and optional co-catalysts is via ion exchange as described inpreviously incorporated U.S. patent application Ser. No. 12/178,380.Various coals deficient in ion-exchange sites can be pre-treated tocreate additional ion-exchange sites to facilitate catalysts loadingand/or association. Such pre-treatments can be accomplished by anymethod known to the art that creates ion-exchange capable sites and/orenhances the porosity of a coal feed (see, for example, previouslyincorporated U.S. Pat. No. 4,468,231 and GB1599932). Often,pre-treatment is accomplished in an oxidative manner using any oxidantknown to the art.

Any suitable methods known to those skilled in the art may be utilizedfor blending various particulates for preparing the biomass feedstockand carbonaceous feedstock. Such methods include, but are not limitedto, kneading, and vertical or horizontal mixers, for example, single ortwin screw, ribbon, or drum mixers.

Ultimately, the biomass feedstock and carbonaceous feedstocks may bedried, under a flow of an inert gas, with a fluid bed slurry drier(i.e., treatment with superheated steam to vaporize the liquid), or theremaining liquids evaporated to provide feedstocks having a residualmoisture content of, for example, less than about 8 wt %, or less thanabout 6 wt %, or less than about 4 wt %.

The each of the biomass feedstocks and carbonaceous feedstocks can bestored for future use or transferred to a feed operation forintroduction into the reactor (100) or gasifier (200). Each feedstockcan be conveyed to storage or feed operations according to any methodsknown to those skilled in the art, for example, a screw conveyer orpneumatic transport.

EXAMPLES Example 1 Feedstock Preparation

As-received coal (Powder River Basin) can be stage-crushed to maximizethe amount of material having particle sizes ranging from about 0.85 toabout 1.4 mm. The crushed coal can be slurried with an aqueous solutionof potassium carbonate, dewatered, and dried via a fluid bed slurrydrier to yield a catalyzed feedstock.

Switchgrass can be dried and crushed to produce a particulate having anaverage size of about 250 microns to provide a biomass feedstock.

Example 2 Catalytic Gasification

The switchgrass particulate of Example 1 can be provided to a combustionreactor fed by an enriched oxygen source. The resulting exhaust gas fromthe combustion reactor could contain hot CO₂. The exhaust gas can bepassed through a heat exchanger in contact with water to produce steam.The generated steam can be superheated and then introduced to afluidized bed gasification reactor (catalytic gasifier) supplied withthe catalyzed feedstock of Example 1. The catalyzed feedstock can beintroduced under a positive pressure of nitrogen. Typical conditions forthe catalytic gasifier could be: total pressure, 500 psi andtemperature, 1200° F. The effluent of the catalytic gasifier couldcontain methane, CO₂, H₂, CO, water, H₂S, ammonia, and nitrogen, whichis passed to a scrubber to remove ammonia and an acid gas removal unitto remove H₂S and CO₂. The CO₂ can be recovered.

1. A process for converting a carbonaceous feedstock into a plurality ofgaseous products, the process comprising the steps of: (A) supplying abiomass feedstock to a reactor; (B) at least partially combusting thebiomass feedstock in the reactor in the presence of an oxygen-containinggas and under suitable temperature and pressure to generate heat energy;(C) utilizing the heat energy to generate steam; (D) introducing aparticulate carbonaceous feedstock, an alkali metal gasificationcatalyst, and at least a portion of the steam to a gasifier; (E)reacting the carbonaceous feedstock in the gasifier in the presence ofthe steam and the alkali metal gasification catalyst and under suitabletemperature and pressure to form a gas stream comprising a plurality ofgaseous products comprising methane and at least one or more ofhydrogen, carbon monoxide, carbon dioxide, hydrogen sulfide, ammonia andother higher hydrocarbons; and (F) at least partially separating theplurality of gaseous products to produce a product stream comprising apredominant amount of one of the gaseous products.
 2. The process ofclaim 1, wherein an exhaust produced from the at least partialcombustion of the biomass feedstock is provided to the gasifier and thegas stream comprises carbon dioxide generated from the at least partialcombustion of the biomass feedstock and the catalytic gasification ofthe carbonaceous feedstock.
 3. The process of claim 1, wherein the gasstream comprises carbon monoxide and hydrogen.
 4. The process of claim1, wherein the reactor is a second gasifier or an oxygen combustor. 5.The process of claim 1, wherein the alkali metal gasification catalystcomprises a source of at least one alkali metal and is present in anamount sufficient to provide, in the carbonaceous feedstock, a ratio ofalkali metal atoms to carbon atoms ranging from 0.01 to about 0.08. 6.The process of claim 1, wherein the steam is generated within thereactor.
 7. The process of claim 1, wherein the heat energy istransferred to a heat exchanger in contact with a water source toproduce the steam.
 8. The process of claim 1, wherein the biomassfeedstock is in a particulate form.
 9. The process of claim 1, whereinthe biomass feedstock comprises an aqueous slurry.
 10. The process ofclaim 1, wherein the product stream comprises a predominant amount ofmethane.
 11. A process for converting a carbonaceous feedstock into aplurality of gaseous products, and generating electricity, the processcomprising the steps of: (A) supplying a biomass feedstock to a reactor;(B) at least partially combusting the biomass feedstock in the reactorin the presence of an oxygen-containing gas and under suitabletemperature and pressure to generate heat energy; (C) utilizing the heatenergy to generate steam; (D) dividing the steam into at least a firststeam stream and a second steam stream; (E) introducing the first steamstream, a carbonaceous feedstock and an alkali metal gasificationcatalyst to a gasifier; (F) introducing the second steam stream to asteam turbine to generate electricity; (G) reacting the carbonaceousfeedstock in the gasifier in the presence of the first steam stream andthe alkali metal gasification catalyst and under suitable temperatureand pressure to form a gas stream comprising a plurality of gaseousproducts comprising methane and at least one or more of hydrogen, carbonmonoxide, carbon dioxide, hydrogen sulfide, ammonia and other higherhydrocarbons; (H) at least partially separating the plurality of gaseousproducts to produce a product stream comprising a predominant amount ofone of the gaseous products.
 12. The process of claim 11, wherein anexhaust produced from the at least partial combustion of the biomassfeedstock is provided to the gasifier and the gas stream comprisescarbon dioxide generated from the at least partial combustion of thebiomass feedstock and the catalytic gasification of the carbonaceousfeedstock.
 13. The process of claim 11, wherein the gas stream comprisescarbon monoxide and hydrogen.
 14. The process of claim 11, wherein thereactor is a second gasifier or an oxygen combustor.
 15. The process ofclaim 11, wherein the alkali metal gasification catalyst comprises asource of at least one alkali metal and is present in an amountsufficient to provide, in the carbonaceous feedstock, a ratio of alkalimetal atoms to carbon atoms ranging from 0.01 to about 0.08.
 16. Theprocess of claim 11, wherein the steam is generated within the reactor.17. The process of claim 11, wherein the heat energy is transferred to aheat exchanger in contact with a water source to produce the steam. 18.The process of claim 11, wherein the biomass feedstock is in aparticulate form.
 19. The process of claim 11, wherein the biomassfeedstock comprises an aqueous slurry.
 20. The process of claim 11,wherein the product stream comprises a predominant amount of methane.